Close monitoring of vital physiological parameters is often key in following the evolution of certain medical conditions (e.g., diabetes, infections, post-operative status or post-traumatic injury). The allocation of trained medical staff and specialized equipment is, therefore, necessary and often translates into a clinical and economic burden on modern healthcare systems. As a growing field, transient electronics may establish fully bioresorbable medical devices capable of remote real-time monitoring of therapeutically relevant parameters. These devices could alert remote medical personnel in case of any anomaly and fully disintegrate in the body without a trace. Unfortunately, the need for a multitude of biodegradable electronic components (power supplies, wires, circuitry) in addition to the electrochemical biosensing interface has halted the arrival of fully bioresorbable electronically active medical devices. In recent years molybdenum (Mo) and tungsten (W) have drawn increasing attention as promising candidates for the fabrication of both energy-powered active (e.g., transistors and integrated circuits) and passive (e.g., resistors and capacitors) biodegradable electronic components. In this review, we discuss the latest Mo and W-based dissolvable devices for potential biomedical applications and how these soluble metals could pave the way towards next-generation fully transient implantable electronic systems.

Catalyzing biochemical reactions with enzymes and communicating with neighboring cells via chemical signaling are two fundamental cellular features that play a critical role in maintaining the homeostasis of organisms. Herein, we present an artificial enzyme (AE) facilitated signal transfer between artificial cells (ACs) and mammalian HepG2 cells. We synthesize metalloporphyrins (MPs) based AEs that mimic cytochrome P450 enzymes (CYPs) to catalyze a dealkylation and a hydroxylation reaction, exemplified by the conversion of resorufin ethyl ether (REE) to resorufin and coumarin (COU) to 7‐hydroxycoumarin (7‐HC), respectively. The AEs are immobilized in hydrogels to produce ACs that generate the two diffusive fluorophores, which can diffuse into HepG2 cells and result in dual intracellular emissions. This work highlights the use of AEs to promote AC to mammalian signal transfer, which opens up new opportunities for integrating the synthetic and living world with a bottom‐up strategy.

Bioresorbable electrochemical sensors remain mostly unexplored despite their ability to provide continuous in situ measurements of critical biomarkers. The primary challenge arises from the direct exposure of the electrodes’ thin metal films to biofluids, which poses difficulties in ensuring both proper operational lifetimes and sensing performance. Molybdenum (Mo) presents itself as a promising biometal due to its uniquely gradual dissolution in biofluids, facilitated by the formation of a slower‐dissolving MoO_x surface layer. Consequently, carefully engineered MoO_x films can endow transient electrochemical sensors with unparalleled stability during extended operational lifetimes. Herein an unprecedented sensor architecture achieved via the unique pairing of sputtered Mo and MoO_x thin films, probed as a pH and dissolved oxygen sensor is reported. Compared to a bare Mo electrode, a bilayer Mo+MoO_x electrode subjected to post‐deposition annealing (400 °C, 60 min, N₂ environment) displayed a largely improved stability (>24 h) in solution and demonstrated predictable functionality during ongoing film dissolution at 37 °C. Collectively, this work establishes a pioneering strategy for the fabrication of reliable and clinically relevant implantable electrochemical sensors.

This work presents the application of ZnO and ZnFe₂O₄ for electrochemical pH sensing. ZnO and ZnFe₂O₄ are synthesized by auto combustion synthesis method. FESEM images revealed that ZnO particles have pyramid and spherical shaped morphology with micrometer dimensions while ZnFe₂O₄ particles have spherical shape at the nanoscale. The surface modified screen-printed electrodes with ZnO and ZnFe₂O₄ particles are initially characterized by the ferri/ferrocyanide redox couple. Significant improvement in sensitivity (bare carbon: 6.3 ± 0.4 μA/mM, ZnO: 8.5 ± 0.3 μA/mM, ZnFe₂O₄: 8.9 ± 0.5 μA/mM) and rate constant (bare carbon: 10 ± 1 ms^-1, ZnO: 46 ± 4 ms^-1, ZnFe₂O₄: 42 ± 3 ms^-1) is observed with the surface modified sensors. Chronopotentiometric pH response of the sensors showed hysteresis behavior with pH loop. No interference effects are observed, and the pH sensitivity of the bare carbon sensor (23.9 ± 1.4 mV/pH) is increased by the introduction of ZnO (38.1 ± 1.3 mV/pH) and ZnFe₂O₄ (37.2 ± 1.1 mV/pH) particles. Stability of the pH response is discussed and ways for its improvement are proposed.

Bioresorbable metals and oxides are central to developing active transient implants, but their exposure to harsh biofluids challenges long‐term functionality due to ongoing dissolution. Biodegradable metal alloys have been proposed to improve corrosion resistance, though research has mainly focused on passive systems based on Mg, Zn, and Fe. Even though Mo and W exhibit superior corrosion resistance and gradual biodissolution among resorbable metals, their application as active sensing materials remains largely unexplored. This work presents a pioneering investigation into the electrochemical stability and sensing performance of Mo–W thin film electrodes. A key factor contributing to the unique stability of alloys is their ability to form stable passivating films which mitigate galvanic interactions. The self‐healing properties of these layers further enhance the electrode's durability. In this work we demonstrate that a nanometre‐thin crystalline WO _x coating significantly enhances the electrochemical stability of Mo–W‐based electrodes and enables reliable oxygen (−9.0 ± 0.2 µA/%O ₂ ) and pH (−33.0 ± 0.2 mV/pH) sensing for up to 10 days in simulated body conditions. Our findings establish Mo and W mixtures with an engineered surface oxide coating as a highly promising avenue for extending the operational lifetimes of bioresorbable implants, an essential step forward toward achieving clinical applicability.